The biggest problem I've seen with 4e is it has the EQ2 syndrome.
EverQuest 1 wasn't balanced. It was far from it. One class was good at soloing, another had to have a group to function, another had three times as many hitpoints as the next best capable in her role, etc. But, it was fun. It was similar to 4e that everything had to be stretched out: Mana regen was so slow you had to wait 10 minutes between fights, then blow your load in 2 minutes. A very fun game, and probably the premier influence on today's mmos.
Everquest 2 aimed to fix that problem. They rebalanced all the classes and races and abilities. They made sure every healer could do their job thoroughly, everyone felt useful, etc. EQ2 was fun, don't get me wrong, but it's predecessor had more subscribers, and it felt empty. It didn't feel plausible, as much as shooting lightning from your fingertips can be, at least.
I think Fourth Ed has the same issue. Yes, the classes are balanced and everything seems to work fluidly. The rules are great. I love how they streamlined everything. People seem to be having fun; the pre-games I've been involved in were fast paced, fun and adventurous. However, It felt like you didn't really matter: as my friend suggested, too cookie cutter.
I'm a big fan of D&D and 4e. I've invested time, money and interest in 4e by promotion, creating the character sheets and earnestly trying to make it a better game. However, I'm still cautious at it's potential. I'm waiting to see what sort of supplements are released for the game.
I imagine when I played 3e core it may have felt the same: New and impressive, but not too many option. Once we see everything 4e has to offer it may change my opinion, but as is I'm disappointed at how little ability one character really has. The sheer lack of abilities per character, even at level 30, the changed power scale, and a few other little things that I need to get used to are abruptly halting my fun.